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  • 1
    Electronic Resource
    Electronic Resource
    The effects of dihydralazine, labetalol and magnesium sulphate on the isolated, perfused human placental cotyledon (1994)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 101 (1994), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective To assess the effects of dihydralazine, labetalol and magnesium sulphate on the vascular tone in the isolated, perfused human placental cotyledon.Methods In vitro perfusion of the fetal compartment of isolated, human placental cotyledons.Results None of the drugs affected basal vascular tone. The thromboxane A2-mimic U46619 and endothelin-1 induced a concentration-dependent increment in perfusion pressure, while 5- hydroxytryptamine induced a variable increase, and norepinephrine induced a small, transient increase in perfusion pressure. After preconstriction with U46619, magnesium sulphate (1.5×10−3 to 6.10−3 mol/1) induced a decrease in perfusion pressure, while dihydralazine (10−6to 10−4 mol/1) or labetalol (10−7 to 10−4 mol/1) enhanced the perfusion pressure. These effects of dihydralazine and labetalol were unaffected by treatment with indomethacin 10−6 mol/1, but could be reversed by addition of magnesium sulphate 6.10−3 mol/1. Labetalol 10−6 to 10−4 mol/1 also caused an increase in the perfusion pressure induced by endothelin-1, but showed no effects after preconstriction with 5-hydroxytryptamine. Pretreatment with labetalol 10−4 mol/1 inhibited the transient increase in perfusion pressure induced by norepinephrine 3.10−5 mol/1.Conclusions The present data demonstrated that the commonly used vasodilating agents labetalol and dihydralazine do not produce vasodilatation in the human perfused cotyledon after vasoconstriction induced by agents of suggested importance for maintenance of fetal placental vascular tone, and that high concentrations of these drugs may even enhance vasoconstriction induced by thromboxane and endothelin-1 in this area. Magnesium sulphate may show the potential to reverse such unwanted effects of dihydralazine and labetalol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1994.tb13548.x
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  • 2
    Electronic Resource
    Electronic Resource
    PROTECTING BEIJLNG'S MUNICIPAL WATER SUPPLY THROUGH WATERSHED MANAGEMEN AN ECONOMIC ASSESSMENT (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 37 (2001), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Watersheds above the Miyun reservoir, a principal source of surface water for Beijing, are designated to be managed for water production, but under the principle of multiple use. Because of the scarcity of arable land, these watersheds cannot be managed only for drinking water. Efforts are under way to reduce sediment delivery, improve the quality of water entering Miyun reservoir, and improve the welfare of watershed inhabitants. An economic appraisal of a watershed management project for the 3,298-ha Shixia watershed above the Miyun reservoir, indicates a 24 percent economic rate of return on the investment made in the project. The net present value (NPV) of the project, calculated at a discount rate of 10 percent, is approximately US$3.49 million. Sensitivity analyses indicate that a doubling of labor costs lowers the NPV to US$2.07 million and a 10 percent decrease in benefits lowered the NPV to US$2.87. It is concluded that the implementation of conservation practices on the Shixia Demonstration Watershed represent an economically efficient use of resources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.2001.tb05495.x
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  • 3
    Electronic Resource
    Electronic Resource
    A NEW METHOD FOR COMBINED ISOMETRIC AND ISOBARIC PHARMACODYNAMIC STUDIES ON PORCINE CORONARY ARTERIES (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 25 (1998), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The principal aim of the present study was to explore the isometric and isobaric capacity of a new intravascular technique, impedance planimetry, in basic pharmacodynamic investigations on porcine isolated epicardial coronary arteries.2. The balloon-based catheter technique provides simultaneous measurements of luminal cross-sectional area and pressure. Sources of errors that may influence the accuracy of measurements were evaluated in detail.3. Under isometric conditions, the stretch ratio-tension diagram showed typical developments of resting and active tensions of the smooth muscle when exposed to alternating maximal K+ depolarization and mechanical stretching. The mean (±SEM) maximum active tension was 28.43 ± 1.72 mN/mm, which was reached at a stretch ratio of 1.26 ±0.02, corresponding to a resting tension of 10.50±0.53 mN/mm (n= 7). The concentration-response relationship to K+ at optimal basal tension was characterized by a mean (±SEM) pD2 value of 1.67±0.01 (n= 7). 4. Under isobaric conditions in the pressure range 40-140 mmHg, the method allowed the investigation of active vascular responses to partial K depolarization. The maximal active response to 25 mmol/L K+ was found at the transmural pressure of 60 mmHg (n= 7). To obtain full K+ concentration-response curves, a basal tension corresponding to a transmural pressure of 120 mmHg was required. The mean (±SEM) pD2 value for the concentration-response relationship to K+ was 1.53±0.01 (n= 10).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1998.tb02344.x
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  • 4
    Electronic Resource
    Electronic Resource
    Naviculo-cuneiform coalition (1978)
    Springer
    International orthopaedics 1 (1978), S. 299-301 
    Details
    ISSN: 1432-5195
    Keywords: Navicular bone ; Cuneiform bone ; Tarsus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Présentation de deux cas de synostose cunéoscaphoïdienne. L'un des malades avait une synostose entre le scaphoïde et les 1er et 3ème cunéiformes, s'accompagnant de lésions dégénératives au niveau du tarse. L'autre présentait une fusion du scaphoïde et du 1er cunéiforme, sans signe radiologique d'arthrose. Les auteurs discutent la pathogénie des altérations arthrosiques du pied et soulèvent l'hypothèse que la maladie de Köhler du scaphoïde tarsien puisse en être la cause première.
    Notes: Summary Two cases of bilateral coalition between the navicular and the cuneiform bones are reported. One patient had coalition between the navicular and the first and third cuneiform with degenerative changes in the tarsus. The other patient had coalition between the navicular and the first cuneiform, but no radiographic evidence of osteoarthritis. The possible pathogenesis of the changes in the feet is discussed, and Köhler's disease of the navicular is suggested as the primary cause.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572255
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  • 5
    Electronic Resource
    Electronic Resource
    Endoscopic Sclerotherapy in Porcine Esophagus Changes Luminal Cross-Sectional Area and Wall Distensibility Dose- and Time-Dependently (1998)
    Springer
    Digestive diseases and sciences 43 (1998), S. 521-528 
    Details
    ISSN: 1573-2568
    Keywords: BIOMECHANICS ; DOSE-RESPONSE RELATIONSHIP ; LONGITUDINAL STUDIES ; SCLEROTHERAPY ; SWINE ; WALL TENSION
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The dose- and time-dependent effects ofendoscopic sclerotherapy on luminal cross-sectional areaand wall distensibility were studied in pigs at 5 and 12cm proximal to the gastroesophageal junction by means of impedance planimetry. Sixteen healthyanimals underwent two sessions of endoscopicsclerotherapy two weeks apart with injections of either5 or 10 ml of 1% Polidocanol in the distal 7 cm of the esophagus each time. The animals wereinvestigated before sclerotherapy, two weeks after eachsession, and finally six weeks after the last session.Six healthy animals were studied as controls. Endoscopic sclerotherapy caused luminal narrowing in thesclerosed zone followed by normalization six weeks afterthe last treatment (P 〈 0.05 in both groups). Walldistensibility decreased in the sclerosed zone after treatment with 10 ml sclerosant (P 〈0.05) followed by partial normalization, while no effectwas found after 5 ml sclerosant (P 〉 0.2).Progressive dilations were observed in the proximalesophagus in both groups and were most pronounced in the10 ml group (P 〈 0.05). Wall distensibility did notchange proximal to the site of sclerotherapy in eithergroup (P 〉 0.1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018802922374
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  • 6
    Electronic Resource
    Electronic Resource
    Biomechanical characteristics of the human esophagus (1993)
    Springer
    Digestive diseases and sciences 38 (1993), S. 197-205 
    Details
    ISSN: 1573-2568
    Keywords: esophageal distensibility ; circumferential wall tension ; wall stiffness ; cross-sectional area ; field gradient principle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Biochemechanical wall properties of the human esophagus were studied. A probe, with a balloon designed for simultaneous measurement of cross-sectional area and intraluminal pressure, was placed in the esophagus 30 cm from the incisors. Tone was not detected before inflation of the balloon. When the balloon was inflated stepwise with pressures up to 40 cm H2O (30.7 mm Hg), measurement of cross-sectional area allowed calculation of distensibility and circumferential wall tension. Balloon cross-sectional area increased linearly with increased balloon pressure. Balloon distension induced contractions, both proximal to the balloon and at the site of distension, at a balloon pressure of about 15 cm H2O (11.5 mm Hg). The cross-sectional area for the threshold for distension induced contractions was 153±12 mm2 (diameter 14 mm). At the onset of these contractions, the contraction force was 15–20 cm H2O (11.5–15.3 mm Hg) and it increased to 47–58 cm H2O (36.1–44 mm Hg) at a balloon pressure of 20–40 cm H2O (15.3–30.7 mm Hg). Circumferential wall tension increased with increasing intraluminal pressure in an almost exponential manner. The pressure elastic modulus increased steeply at lower balloon pressures (10–20 cm H2O) (7.7–11.5 mm Hg), but at higher balloon pressures (20–40 cm H2O) (15.3–30.7 mm Hg) this increase was less. The circumferential wall tension and wall stiffness of the human esophagus increased with increasing balloon pressure and cross-sectional area. When a threshold is reached, distension induced contractions both proximal and distal to the balloon and at the distension site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307535
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  • 7
    Electronic Resource
    Electronic Resource
    Histomorphometry and Strain Distribution in Pig Duodenum with Reference to Zero-Stress State (2000)
    Springer
    Digestive diseases and sciences 45 (2000), S. 1500-1508 
    Details
    ISSN: 1573-2568
    Keywords: morphology ; biomechanics ; mucosal compression ; residual strain ; small intestine ; opening angle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The morphometry at no-load and zero-stress states and residual circumferential strains were determined along the pig duodenum in vitro in seven pigs. The no-load state was obtained by cutting eleven 2-mm-wide rings at 10% intervals along the duodenum. The zero-stress state was obtained by cutting the rings radially. The zero-stress state provides a standard morphological state to describe tissue since internal and external forces do not affect the tissue. The morphometric measures were obtained from digitized images, and the layer thicknesses were measured from histological sections. The mucosal and serosal circumferences, the wall thickness, and the wall thickness-to-mucosal radius ratio were largest in the proximal end of the duodenum (f 〉 1.9, P 〈 0.05). The thickness of the submucosal stratum compactum layer and the opening angle increased in distal direction (f = 2.3, P 〈 0.05 and f = 6.5, P 〈 0.001). The residual strain at the mucosal surface was negative, indicating that the mucosa–submucosa layers of duodenum in no-load state are in compression. Distension experiments showed that the residual strain makes the stress distribution through the wall more uniform in the pressurized state. In conclusion, the large circumferential residual strains must be taken into account in the study of physiological problems, in which the stresses and strains are important, eg, the bolus transport function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005592306587
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  • 8
    Electronic Resource
    Electronic Resource
    Impedance Planimetric Characterization of Esophagus in Systemic Sclerosis Patients with Severe Involvement of Esophagus (1997)
    Springer
    Digestive diseases and sciences 42 (1997), S. 2317-2326 
    Details
    ISSN: 1573-2568
    Keywords: ESOPHAGUS ; SYSTEMIC SCLEROSIS ; CROSS-SECTIONAL AREA ; DISTENSIBILITY ; MANOMETRY ; TENSION
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study was designed to evaluate thedistensibility and secondary peristalsis of theesophagus in patients suffering from systemic sclerosiswith severe esophageal involvement. Balloon distensionwith impedance planimetric measurement of luminalcross-sectional area was done 7 and 15 cm above thelower esophageal sphincter in 13 patients and ninehealthy controls. The controls were studied both with and without receiving the anticholinergic drugbutylscopolamine. The cross-sectional area-pressurerelations were nonlinear with the largestcross-sectional area in patients at both measuring siteswhen compared to controls (P 〈 0.001). Theanticholinergic drug butylscopolamine increased thecross-sectional area in controls (P 〈 0.001). Thecross-sectional area distensibility, defined asCSA0 -1 ΔCSA ΔP-1 did not differ betweenpatients and controls. Balloon distensions elicitedcontractions proximal to the distension site. Theamplitude and frequency of contractions at the distaldistension site were significantly reduced in the patients whencompared to the controls (P 〈 0.05). In conclusion,the distal esophagus is most severely affected inpatients with systemic sclerosis with increased cross-sectional area and impairedperistalsis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018831104549
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